The present technology relates to a reverse printing ink composition used for forming, for example, an organic layer of an organic EL (Electroluminescence) display unit, a printing method using the same, and a method of manufacturing a display unit using the same.
As development of information and communications industry has been accelerated, display devices having high performance have been demanded. For example, an organic EL (Electroluminescence) display device is a self light emitting type display device, and is superior in its wide view angle, contrast, and response speed.
Materials of a light emitting layer and the like forming the organic EL device are broadly classified into a low-molecular material and a polymer material. The low-molecular material is formed mainly by a dry method (evaporation method) such as a vacuum evaporation method. The polymer material is formed mainly by a wet method such as spin coating, an ink jet method, nozzle coating, relief printing, and reverse offset printing. In view of practical utility and cost of materials, the following method has been proposed (for example, see Japanese Patent Nos. 4062352 and 3899566). In such a method, a red light emitting layer and a green light emitting layer are formed by patterning with the use of a wet method, and a blue light emitting layer as a common layer is formed over the red light emitting layer and the green light emitting layer by an evaporation method. As a method of forming the red light emitting layer and the green light emitting layer by patterning, a reverse offset printing method is often used due to its low cost (for example, see Japanese Unexamined Patent Application Publication Nos. 2005-310465 and 2005-126608).
Reverse offset printing is performed by the following steps. First, the entire surface of a blanket is coated with ink (obtained by dissolving component materials of a red light emitting layer or a green light emitting layer in a solvent) to form a transfer layer. Next, the transfer layer is brought into contact with a reverse printing plate in which concave sections of a pattern corresponding to the light emitting layer to form a pattern layer on the blanket. In the pattern layer, patterning is made according to the concave sections of the printing plate. Finally, the blanket in which the pattern layer is formed is brought into contact with a substrate to be printed, and thereby printing of the red light emitting layer or the green light emitting layer is performed.